CVE-2026-123596
Hickory DNS through 0.26.0-alpha.1 DNSSEC Validation Bypass via Ancestor-Delegation NSEC
Hickory DNS hickory-proto through 0.26.0-alpha.1 and hickory-net 0.26.0-beta.1 before 0.26.2 contain a DNSSEC validation flaw in the validating recursor's NSEC handler that accepts parent-side ancestor-delegation NSEC records as proof of nonexistence for names below the zone cut. An on-path attacker, rogue parent nameserver, or attacker winning a port and TXID race can deliver one forged NXDOMAIN response built from genuinely signed parent NSEC records, causing authenticated denial of existing child-zone names cached for the negative TTL.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| hickory-dns hickory-dns hickory-proto
cargo |
≥ 0; ≤ 0.26.0-alpha.1 (affected, semver)
Other versions: unaffected |
CNA: VulnCheck |
| hickory-dns hickory-dns hickory-net
cargo |
≥ 0.26.0-beta.1; < 0.26.2 (affected, semver) 0.26.2 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 8.7 high |
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 8.8 high |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/hickory-dns/hickory-dns/security/advisories/GHSA-3r6v-f3jh-vvqmCNA: VulnCheck · vendor-advisory
- https://www.vulncheck.com/advisories/hickory-dns-through-0.26.0-alpha.1-dnssec-validation-bypass-via-ancestor-delegation-nsecCNA: VulnCheck · third-party-advisory
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